[OZAPRS] Why we don't always make it...

Terry Neumann tfneumann at internode.on.net
Sat Feb 18 12:21:59 EST 2012


On 17/02/2012 8:21 AM, ozaprs-request at aprs.net.au wrote:
> Message: 1
> Date: Thu, 16 Feb 2012 19:46:28 +1100
> From: "Nic McLean"<mcleannb at bigpond.com>
> To:<ozaprs at aprs.net.au>
> Subject: [OZAPRS] No recent positions on Googlemaps.
> Message-ID:<000001ccec87$7bb3e8f0$731bbad0$@bigpond.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi,
>
> Does anyone on the list know why aprs positions aren't making it from RF to
> googlemaps?
>
> Best 73's
>
> Nic
>
> VK5ZAT
G'day Nic,

Additional to what Tony has already offered, there can be other reasons 
why we sometimes won't be seen on APRS servers,

1) The path you set for your packets may not be "sufficient" to survive 
the number of hops needed to make it to an Igate.   Check up that you 
have this correctly according to the published recommendations.

2) Congestion on the frequency can be a real issue in my observation / 
experience, especially if there are a large number of (fixed) stations 
transmitting information.   I am sometimes quite surprised at how much 
of this there is - at least from my QTH.   In the midst of all of this 
your beacons may simply be swamped by some of this traffic especially 
if, as a mobile station running (probably) lower power and the 
constraints of mobile antennas, you are competing with all the 
advantages of base stations in locations with a large spread.  The 
'hidden transmitter" issue present right from the early days of packet 
radio is nearly always with us.   Throw in random geographical barriers 
and it all becomes a game of chance.

I know in my own travels it's not uncommon to be "un-noticed" by the 
system in my trips around this area if I haven't turned my own 
digipeater on - even when one might expect otherwise.      I only run 5 
watts in the car and I know that sometimes I can drive for 25 or 30 
minutes through locations where one would expect to 'make it' and miss 
out altogether until I come within the range of my own or some other 
digi where I acquire a certain RF priority.

As Tony says, given all of these challenges, it's amazing that the 
system works as well as it does.

73
Terry

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